1. Field of the Invention
The present invention relates generally to a heat sink and fabrication method thereof, and more particularly, to a heat sink having supporting columns and a method for fabricating the same.
2. Description of Related Art
With the rapid development of integrated circuit design and fabrication technology, the level of integration of integrated circuits increases. Accordingly, how to efficiently dissipate heat generated by the integrated circuits during operation has become much more critical. Generally, heat sinks are disposed on the integrated circuits for heat dissipation. Heat sinks are made of materials that can absorb and dissipate heat efficiently. To further improve heat dissipating efficiency, heat sinks can be used in combination with fins, fans or liquid cooled structures. The heat sinks, if used in combination with liquid cooled structures, can obtain better heat dissipating efficiency.
FIG. 3A is an exploded diagram of a conventional liquid cooled heat sink 2. The heat sink 2 comprises a lower substrate 21 and an upper substrate 22 opposed to the lower substrate 21. The lower substrate 21 has a concave portion 211 and a plurality of supporting columns 23 formed on the concave portion 211 of the lower substrate 21 for supporting the upper substrate 22. A through hole 221 is formed at a corner of the upper substrate 22. Referring to FIG. 3B, after the lower substrate 21 and the upper substrate 22 are tightly fixed together through fixing components (not shown) or by a soldering mechanism, the supporting columns 23 can effectively support the upper substrate 22. Therefore, a cooled liquid 25, after injected through the through hole 221 into a receiving space 24 formed between the upper substrate 22 and the lower substrate 21 and the through hole 221 is sealed, dissipate heat by transforming itself from a vapor state into a liquid state and vice versa according to different working temperatures.
The fabrication method for fabricating the supporting columns 23 is shown in FIG. 4. Aggregate is continuously deposited on the concave portion 211 of the lower substrate 21 at positions where the supporting columns 23 are to be formed until the aggregate has a height equal to a certain level such that cone-shaped supporting columns 23 can be obtained. However, in the above fabrication process, the density of a capillary structure of the supporting columns 23 is difficult to be controlled and the capillary structure is easy to be broken, thereby resulting in a low density capillary structure of the supporting columns 23. The low density of the capillary structure further leads to small capillary forces to absorb the cooled liquid 25 injected into the receiving space 24. Thereby, the circulation efficiency of the cooled liquid 25 in the receiving space 24 is adversely affected, that is, the heat circulation efficiency is adversely affected.
Furthermore, as shown in FIGS. 3A and 3B, because surface 222 of the upper substrate 22 contacts with nothing but top portions 231 of the supporting columns 23 only, it leads to low strength of combining structure between the surface 222 of the upper substrate 22 and the top portions 231 of the supporting columns 23, and poor continuity of the capillary structure.
Accordingly, there exists a strong need in the art for a heat sink and fabrication method which can control and improve capillary structure and density of the supporting columns so as to increase heat dissipating efficiency of the heat sink.